1. Field of the Invention
The present invention relates to a backlight module for reducing interference, and in particular to a backlight module with a phase control unit, capable of reducing the interference caused by electric leakage.
2. Description of the Related Art
The Cathode Ray Tube (CRT) had been the mainstream in the monitor industry and market for a long time because of its excellent image quality and lower cost. However, with the price of liquid crystal display having dropped to a reasonable level, its shortcomings, such as huge volume and relatively large energy consumption, have caused the CRT to be replaced by the LCD. The liquid crystal molecules in an LCD will not radiate so that the backlight module is required to provide the light source to get sufficient lightness and contrast for revealing the image.
Please refer to FIG. 1A and FIG. 1B, respectively showing the backlight module of the prior art and the driving power source chart of each lamp in the prior art. The lamps L1˜Ln in the backlight module of the prior art are driven by the driving power sources provided by the corresponding inverter D1˜Dn, and the lamps L1˜Ln are under high-voltage starting and high-voltage operating mode. Although between the high voltage terminals of lamps L1˜Ln and the backlight module exist high impedances C1˜Cn, the high-voltage operating in lamps L1˜Ln causes the backlight module to exhibit electric leakage all the time, thus resulting in leakage charges accumulating in the backlight module. Further, the ground terminal of the liquid crystal driving substrate is coupled to the backlight module, so the electric leakage will also cause the ground terminal of the liquid crystal driving substrate to sustain a high voltage effect and become unstable, thus interfering with the frame of the display. As shown in FIG. 1A, the driving power source A1 drives L1, A2 drives L2, and An drives Ln. Because each driving power source, i.e. A1˜An, is an alternating current (AC) voltage with the same phase as seen in FIG. 1B, which shows the driving power sources A1˜An, the electric leakage will be compounded at each time point, causing that the largest electric leakage to occur at time point (T1) and the smallest electric leakage to occur at (T2), thus generating the phenomenon of ripples and interfering with the frame of display. In order to overcome this problem, the present invention provides a backlight module for reducing interference that carries out a phase shifting of each driving power source so as to get the effect of reducing interference caused by electric leakage.